A liquid crystal display device has a liquid crystal panel and a light-emitting device that is arranged at the rear of the liquid crystal panel and illuminates the liquid crystal panel from behind. The light-emitting device for a liquid crystal display device is also referred to as a planar light unit or backlight. The light-emitting device for a liquid crystal display device includes a side edge type light-emitting device that causes light that enters from a plurality of LEDs arranged on the side surface of a flat plate-shaped light guide plate to exit from the main surface and a directly under type light-emitting device that directly causes light radiated from a plurality of LEDs arrayed in the form of a plane to travel upward. The side edge type light-emitting device can be easily reduced in thickness and can reduce the number of LEDs that are used by reducing the number of arranged LEDs to a comparatively small number. On the other hand, it is not easy to reduce the size of the directly under type light-emitting device, but it is easy to reduce the weight since no light guide plate is used.
Patent Document 1 describes a light source device that emits light in the form of a plane by arranging a plurality of light-emitting element modules having an LED and a light-diffusing lens in the form of a matrix. The light source device described in Patent Document 1 is characterized in that the light distribution characteristics of adjacent light-emitting element modules are different from each other.
Further, Patent Document 2 describes a backlight system that makes adjustment of a visual field easy as well suppressing a reduction in total efficiency by collimating light that exits from point light sources arranged in the form of an array by a total reflection lens and diffusing the collimated light.
Further, in the directly under type light-emitting device, the contrast of the liquid crystal display device may be improved and power consumption may be reduced by turning off part of the light-emitting areas or turning on only part thereof (hereinafter, called “local dimming”). In recent years, a high display quality obtained in the directly under type display device is also demanded for a medium/small-sized liquid crystal display device whose main stream is the side edge type light-emitting device.